1. Field of the Invention
The present invention belongs to a technical field in connection with a thin film transistor substrate and a display device.
2. Description of Related Art
In a display device of an active matrix type such as a liquid crystal display, thin film transistor (hereinafter, sometimes called TFT) is used as a switching element. A schematic diagram of a TFT element is shown in FIG. 2. The TFT element includes a gate electrode formed on a glass substrate, a non-doped semiconductor silicon layer provided via a gate insulating film, and impurity-doped semiconductor silicon layers contacted to the non-doped semiconductor silicon layer. Electrical connection with the respective impurity-doped semiconductor silicon layers is made using wiring metal including Al alloy. The wiring metal is referred to as a source electrode or a drain electrode. The drain electrode is further connected with a transparent conductive film used in a liquid crystal display section. As the wiring metal (source electrode or drain electrode), various Al alloys have been proposed (for example, JP-A-7-45555 and JP-A-2005-171378). In such electrical connection, a structure is used, in which a stacked film including high melting point metal such as Mo, Cr, Ti, or W is interposed as barrier metal between the wiring metal and the TFT element (semiconductor silicon layer), or between the wiring metal and the transparent conductive film (hereinafter, sometimes called ITO film) used in the liquid crystal display section to prevent direct contact between them.
Hitherto, various proposals have been made on a technique for omitting the barrier metal between the wiring metal and the ITO film as seen in JP-A-2004-214606, JP-A-2005-303003, and JP-A-2006-23388. However, a technique for omitting the barrier metal between the wiring metal and the TFT element (semiconductor silicon layer) has not been sufficiently investigated.
[Patent literature 1] JP-A-2004-214606
[Patent literature 2] JP-A-2005-303003
[Patent literature 3] JP-A-2006-23388